Atypical beta-adrenoceptors belong to the family of adrenoceptors which mediate the physiological actions of the hormones adrenaline and noradrenaiine. Such receptors have been described for example by J R S Arch et. al., Nature, 309, 163-165 (1984); C Wilson et. al., Eur. J. Pharrnacol., 100, 309-319 (1984); L J Emorine et. al., Science, 245, 1118-1121 (1989); and A. Bianchetti et. al. Br. J. Pharmacol., 100, 831-839 (1990).
Phenethanolamine derivatives having activity at atypical beta-adrenoceptors are disclosed in, for example, European Patent Applications EP-A-0455006 and EP-A-0543662.
Sub-types of the adrenoceptors, .alpha..sub.1 -, .alpha..sub.2 -, .beta..sub.1 -, .beta..sub.2 - and .beta..sub.3 -(atypical) can be identified on the basis of their pharmacological properties and physiological effects. Chemical agents which stimulate or block these receptors (but not .beta..sub.3) are widely used in clinical medicine. More recently, emphasis has been placed upon specific receptor selectivity in order to reduce side effects caused, in part, by interactions with other receptors.
Atypical beta-adrenoceptors are known to occur in adipose tissue and the gastrointestinal tract. Atypical beta-adrenoceptor agonists have been found to be particularly useful as thermogenic anti-obesity agents and as anti-diabetic agents. Compounds having atypical beta-adrenoceptor agonist activity have also been described as being useful in the treatment of hyperglycaemia, as animal growth promoters, as blood platelet aggregation inhibitors, as positive inotropic agents and as antiatheroscierotic agents, and as being useful in the treatment of glaucoma.